Officials have admitted that unit 5 at Fukushima has pipe and support systems that did not meet 2006 anti-quake standards. This includes the main water supply pipes to the reactor. Anti quake standards were raised in 2006, TEPCO acknowledged the increased risk to the reactors but did no reinforcement work. They also did not submit any test results showing the reactors were compliant as is. Apparently TEPCO simply did nothing about the 2006 standards changes. This is in step with our findings of work done in response to the 2007 earthquake at Kashiwazaki-Kariwa. TEPCO was told by NISA to do earthquake upgrades. What was done was highly superficial items like some small tank tie downs and a rail in the control room. In 2007 no work was done to piping and supports per the public reports put out by TEPCO at the time. This leaves two significant official warnings of increased earthquake risk that went largely un-responded to.

Unit 5 is the one of the newer BWR Mark 1 reactors at Fukushima Daiichi. Construction began in 1972, construction on unit 4 began in 1973. Toshiba was the architect and reactor supplier of Unit 5. They also played the same role at unit 3. Unit 5 does feature some design improvements over units 1-4 including the outside vertical concrete beams. Why these changes were not made on the design of unit 4 is unknown.

TEPCO and NISA have been using unit 5 as a testing ground and forensic tool.

“The calculations showed that a strength of between 1.2 to 4.3 times the anti-quake standards would be applied to the main water supply piping as well as support for seven piping systems if the expected quake under the new standards had struck the reactor.”

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